


Newton's Cradle

by PeppyBismilk



Series: Play It Sweet [2]
Category: Yuri!!! on Ice (Anime)
Genre: Alternate Universe - College/University, F/F, Fluff, I Don't Even Know, M/M, Nerdy Dirty Jokes, Sexual Content, Walking In On Someone
Language: English
Status: Completed
Published: 2020-01-03
Updated: 2020-01-03
Packaged: 2021-02-27 11:28:59
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,547
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/22096399
Author URL: https://archiveofourown.org/users/PeppyBismilk/pseuds/PeppyBismilk
Summary: Today, the laws of physics really let Mila down (but really, it's all Seung-gil's fault).Takes place in the same universe asWaiting on a Friendbecause my self control is pretty much non-existent these days.
Relationships: Mila Babicheva/Sara Crispino, Phichit Chulanont/Lee Seung Gil
Series: Play It Sweet [2]
Series URL: https://archiveofourown.org/series/1590445
Comments: 8
Kudos: 27





	Newton's Cradle

Never before in her life had Mila been so happy to see Seung-gil Lee.

“Seung-gil! Just who I was hoping to run into!” 

Eyes narrowed and lips turned down, Seung-gil didn’t look nearly as excited to see her. “What do you want?”

“Well…” For a split-second, Mila considered batting her eyelashes, but Seung-gil was impervious to flirting unless it was Phichit. “I actually need a favor.”

“No,” said Seung-gil. He didn’t even spare her a parting glance before turning down the hall to his wing of the dormitory.

Mila chased after him, speeding up until she was walking in step with him. “Wait! You don’t even know what it is yet.”

“Why would I do you a favor?” Seung-gil didn’t look up when he asked.

Mila clicked her tongue and sighed inwardly. How did Phichit put up with him? He could be such a jerk and, unlike Yuri, he wasn’t even fun to tease. It was impossible to get a rise out of Seung-gil, so she stuck to the facts. “I just wanted to borrow your Physics book for a minute. I left mine at Sara’s and she’s got practice until late, but I need the discussion questions.”

They’d reached Seung-gil’s room, but he turned the key to his door and went in without a word. He flicked on the light, took off his shoes, and put his backpack down. 

“So…” Mila shuffled her feet in the doorway. Phichit wasn’t home, so it was just the two of them. Cold acquaintances. “Is that a no? I'm really not asking a lot here.”

Slowly, Seung-gil headed for his desk. Mila rolled her eyes. She could find someone else; Seung-gil was just the most convenient option, and they were supposed to be friends. 

Just as she turned to leave, Seung-gil thrust the textbook her way. “Make it quick.”

“Thanks,” she said tightly. There was no need to gush when he’d been an ass. “I’ll be right back.”

But Seung-gil had already retreated to the back of his room. 

With another sigh, Mila took the textbook to her own room to confirm the pages for the assignment with her notes, then took a couple pictures of the questions with her phone. Once she made sure they were clear, she closed the book and headed back to return it.

“I should keep it all night just to piss him off,” she muttered. Seung-gil didn’t answer when she knocked on the doorframe, but the door was partially open so she stepped inside. “Told you I’d be qui—SHIT!”

Nothing could have prepared her for what she found: Phichit sprawled out on the bed, naked from the waist down, with Seung-gil crouched in front of him, pushing one of his legs up by the knee. She screwed her eyes shut and tried to bleach her brain, but she could still picture it, sharp enough to paint. Phichit’s leg (and his dick) sticking up in the air, the hem of his shirt pulled up between his teeth, Seung-gil’s fingers deep in his ass—all burned into her retinas.

“I swear to—” Mila chucked the book inside and backtracked into the hallway in one swift motion. “If you can’t keep your hands off each other for five goddamn minutes, at least close your fucking door!”

She slammed it shut for them, ignoring the muffled cry from inside the room.

Why didn’t Professor Feltsman just put discussion questions online like a normal teacher? Why hadn’t Mila just signed up for chemistry like Guang Hong? It would be months before she would be able to look Phichit or Seung-gil in the eye again. 

How were they so quick? Phichit hadn’t even been home when she'd borrowed the book from Seung-gil. And they didn’t even bother closing the door all the way (let alone locking it) before they had at each other!

Mila could have lived her entire life without knowing they were exhibitionists. Although, a far less kinky explanation was completely possible. Seung-gil was a piano prodigy and a math whiz, but he was more than a little absent-minded, especially when it came to his boyfriend. Mila had been at that fateful rehearsal when Seung-gil had first laid eyes on Phichit—the dissonant complaint from the piano when Seung-gil's palms smashed the keys had been kind of cute. He and Phichit had been inseparable ever since. Mila thought they were good for each other and she didn’t mind the incessant public displays of affection, but today had definitely crossed a line. 

At least she hadn’t taken longer; she might have had two friends' dicks to erase from her memory.

Mila shook her head and opened her laptop. Physics. Newton’s Laws of Motion. This was easy stuff. The perfect distraction. She read the picture of the textbook on her phone. 

_1\. Explain how a Newton's cradle demonstrates conservation of momentum and energy._

“Oh, fuck,” Mila muttered. 

_A Newton’s cradle,_ she began typing, _uses a series of swinging balls_

“No!” She jabbed the Backspace key.

_swinging spheres. When a sphere at one end strikes the stationary spheres, it transmits a force through the stationary spheres that pushes the sphere at the opposite end upward._

Good. Nothing sexual about that.

_That sphere swings back and strikes the almost-stationary spheres, repeating the effect in the opposite direction and producing a steady rhythm._

Just bodies colliding rhythmically, in a completely non-sexual way. Next question.

_2\. Why do the balls of the Newton’s cradle stop moving?_

“Can we not call them balls?” she said under her breath.

_In atmosphere, the spheres lose energy to air friction,_

Non-sexual friction.

_the vibrations at the moment they collide produce sound energy,_

Thank god Phichit’s mouth had been full of shirt to muffle his sound energy, and she didn’t even want to think about vibrations in that context. 

Mila blinked hard and pushed on. 

_and they lose energy to heat upon collision._

Oh, there had been plenty of heat energy, all right. “Fuck,” she muttered. “Focus.”

_Each of these factors takes energy away from the sphere, and this loss of energy causes the spheres to slow down and eventually stop._

God, she hoped these thoughts would eventually stop or else she’d have to drop the class. If only there was a law of motion that would help her avoid Phichit and Seung-gil until she stopped picturing them demonstrating those laws. 

Somehow, she got through the questions and managed to distract herself with other assignments until Sara knocked on the door.

“Hey!" Sara kissed Mila and handed her the missing Physics book. “Sorry I couldn’t bring this until now. Did you get your assignment done?” 

Memories came rushing back, and Mila set the book aside with a shudder.

“What’s wrong?” Sara wondered.

Mila could never keep anything from Sara. “I got the questions from Seung-gil but when I went to give him his book back, I walked in on him and Phichit having sex.”

Sara’s eyes went as wide as dinner plates even though Mila spared her the gory details.

“I had his book for _five fucking minutes_ and they couldn’t even—” Mila put up a hand. “You know what, never mind. I’m over it.”

From the look on Sara’s face, she wasn’t. “Hang on. Was it big?”

“Was what big?” Mila frowned as realization dawned. “Oh my god, Sara!”

“What? I’m just curious!” 

And more memories, less lurid ones, flooded Mila’s mind. The whole reason Mila had witnessed Phichit and Seung-gil’s meet cute last year was because Sara had been trying to get closer to Seung-gil. It had all worked out in the end—Phichit and Seung-gil had gotten together and Sara had moved on with Mila.

But Sara was still completely shameless.

Mila groaned. The things she did for her girlfriend. “If you must know, I didn’t see _his_ because _he_ ,” and Mila knew Sara was only interested in one of the men in question, “was facing the other way, thank god.” 

She expected to be met with disappointment, but instead, Sara looked thoughtful. “Yeah, that's about what I thought.”

“Sara!” 

“Sorry, sorry,” Sara said, throwing her arms around Mila. “I was just being nosy, but it’s cute that you’re jealous.”

Now it was Mila’s turn to go wide eyed. “I’m not jealous!” 

“You do know I don’t like Seung-gil that way anymore, right?” Sara cupped Mila’s face and smiled a sweet smile. “I only have eyes for you, no matter how hung he is.”

Sometimes Mila just didn’t know what to do with her. “Um, thanks? I think?” 

“Besides, if I really wanted to know, I’d just ask Phichit,” Sara went on. 

“Oh, god.” Mila cringed and pulled out of Sara’s embrace. Phichit would probably tell her, too; he and Sara were cut from the same incorrigible cloth.

“But,” Sara tapped Mila’s nose, “I’m not going to do that. I would much rather take your mind off of your troubles, if that’s all right with you.”

It was more than all right—Mila had always learned better from practical examples than visuals, and Sara’s excellent demonstration of friction and momentum wiped Mila’s mind clean of the whole ordeal.

At least until the next time she saw Phichit. It was going to take time. Sara was good, but even she couldn’t break the laws of physics. 

**Author's Note:**

> Meanwhile, Phichit was not embarrassed at all.
> 
> This goofy story was going to plague me until I posted it, but 2020 is the year of Post It Anyway and Don't Delete. Life is hard, so I hope it amuses someone out there. 
> 
> I swear I'm not going to let this AU run amok like that other one I wrote.


End file.
